The present invention relates to a method for operating a drive control device and a drive control device operating according to the method, as well as to a computer program for implementing the method and accordingly also to a drive control device having means for executing such a computer program. The invention relates most particularly to a method for operating a drive control device, wherein the latter has an inverter and wherein said inverter comprises semiconductor switches which can be controlled by means of control signals.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
Drive control devices of the aforesaid type are known per se. As a result of the control implemented by means of the control signals the inverters generate an output voltage having variable frequency and voltage. By this means it is possible to adjust and regulate the rotational speed and the torque of e.g. an electric motor as the load of the drive control device. Control electronics for generating the control signals are disposed on a low-voltage side of the drive control device and the inverter is in contrast located on a high-voltage side. An electrical isolation means is provided between the low-voltage side and the high-voltage side for safety reasons. The control signals must nonetheless be transmitted over and beyond said electrical isolation. A serial transmission, inter alia, has been considered for this purpose. A disadvantageous aspect with this approach, however, is that displacement currents can be produced between the high- and low-voltage sides due to high voltage rates of rise during switching of the semiconductor switches. Said currents interfere with the signal transmission and can result in a situation in which it is no longer possible to control the semiconductor switches properly. In order to solve said problem, consideration has been given in the prior art to limiting the bandwidth of the serial transmission to such an extent that an adequate signal-to-noise ratio is established. Security measures, e.g. a telegram repetition, are implemented for other possible sources of interference that may occur, although such measures ultimately have a negative impact on the bandwidth. A separate transmission of the individual control signals is also considered as an alternative. This however means implementing a separate electrical isolation for each control signal, so this alternative turns out to be inflexible and costly.
It would therefore be desirable and advantageous to obviate prior art shortcomings and to provide an improved method for operating a drive control device and a drive control device operating according to the method.